The importance of oral hygiene has grown with the progression in aging. For example, the prevention and treatment of dental decays (cavity) and periodontal diseases is an important objective in oral hygiene. Aging is causing similar problems in pet animals such as dogs and cats as in human. Specifically, the establishment of techniques for preventing or treating periodontal diseases in pet animals has also become an important task. In general, keeping the mouth clean by toothbrushing is believed to be an important daily habit to prevent periodontal diseases and dental decays. However, brushing an animal's teeth is not always easy. Thus, it can also be said that the technology for preventing or treating periodontal diseases in animals is more important than that for humans.
Gingivitis and periodontitis are representative oral diseases, and collectively called “periodontal diseases”. Gingivitis is a disease caused by bacteria in plaques (dental plaques) accumulated on the surface of teeth and periodontal tissues. Gingival swelling and bleeding are observed, but not alveolar bone absorption. In most cases, gingivitis is curable.
In periodontitis, inflammation also spreads to the periodontal membrane and alveolar bone. Periodontitis is a pathological change that results in the disruption of periodontal tissues such as the periodontal membrane and alveolar bone. To date, it is difficult to therapeutically restore destroyed periodontal tissues. Periodontitis is a severe inflammatory disease that ultimately results in tooth exfoliation. Depending on the degree of severity, periodontitis worsens bad breath and causes bleeding, and contact with the teeth becomes unpleasant. In more severe cases, oral pathogenic bacteria circulate within the body via blood stream, and the effects are occasionally observed in the heart, kidney, and others. Multiple factors are suggested to cause periodontal disease. From the point of infection by plaque pathogenic bacteria, periodontal disease is a common disease to human and animals.
The most common causative bacteria of the periodontal disease are black-pigmented Gram-negative anaerobic bacteria. This group of bacteria was formerly classified into the genus Bacteroides, but is currently grouped into the genera Porphyromonas and Prevotella. Although bacterial species that cause the periodontal disease in different animals are slightly different, they all cause the disease in human, dog, cat, sheep, rat, and other animals. In dogs and cats, the proportion of the genus Porphyromonas in bacterial flora of dental plaques occasionally reaches 80%. The most frequently isolated bacterial species is P. gingivalis. P. endodontalis, P. circumdentaria, P. canoris, P. salivosa, and the like are also often isolated. Additional new bacterial species are expected to be isolated in the future.
About 80% of family dogs are believed to have periodontitis. If periodontal disease is not treated, tooth pain and extraction may occur, which significantly reduce the quality of life (QOL) for the pet. During the past several years, chews (gums for pets), treats (snacks), pet food, and the like, containing components for improving their oral hygiene were commercialized one after another. This suggests the growing interest of pets' owners in the periodontal disease of their pets.
Actually, commercial products that are intended to prevent periodontal disease are sold on the market, reflecting such owners' interest. For example, pet food formulated with dietary fibers is assumed to have the effect of preventing periodontal disease by suppressing the deposition of dental plaque and calculus by using the mechanical removing action of mastication. “Hill's Prescription Diet t/d” (trade name) is a pet food product formulated with dietary fibers. Dog tooth paste and the like formulated with enzymes aiming at plaque control have also been developed. Furthermore, there are a supplement (trade name: “Xylitol C”) and pet beverages aiming at oral care that use the synergistic effects of active ingredients such as Biofermentics, vitamin C, oyster extract, xylitol, Sunphenon, and catechin.
In current veterinary clinical practice, periodontal disease is treated by the following methods:
(1) removal of plaque which is the major cause of this disease;
(2) dental scaling (removal of dental calculus);
(3) tooth extraction; etc.
Specifically, the prevention of dental calculus deposition and plaque control are important as post-therapeutic care or preventive method for periodontal disease. Thus, particular formulae of dry pet food having the effect of mechanical removal of dental calculus are one of the effective measures to date. Alternatively, brushing using pet tooth powder is also expected to have therapeutic and preventive effects.    Patent Document 1: Japanese Patent Application Kokai Publication No. (JP-A) 2002-34590 (unexamined, published Japanese patent application)    Patent Document 2: JP-A (Kokai) 2002-34577    Patent Document 3: JP-A (Kokai) 2001-342199    Patent Document 4: JP-A (Kokai) H11-239498    Patent Document 5: JP-A (Kokai) 2005-89301    Non-patent Document 1: Cummins, M. J., Arthritis Rheum., 2003; 49(4): p585-593    Non-patent Document 2: Shiozawa, S., J. Interferon Cytokine Res., 1998; 18(4): p255-262    Non-patent Document 3: Ship, J. A., J. Interferon Cytokine Res., 1999; 19(8): p943-951    Non-patent Document 4: Gilger, B. C., J. Interferon Cytokine Res., 1999; 19(8): p901-905    Non-patent Document 5: Satoh, Y., J. Interferon Cytokine Res., 1999; 19(8): p887-894    Non-patent Document 6: Palomba, M., Clin. Ter., 2000; 151(1 Suppl. 1): p59-61    Non-patent Document 7: Lecciones, J. A., J. Interferon Cytokine Res., 1998; 18(9): p647-652    Non-patent Document 8: Lecce, J. G, Mol. Biother., 1990; 2(4): p211-216    Non-patent Document 9: Young, A. S., Parasitology, 1990; 101(2): p201-209    Non-patent Document 10: Tompkins, W. A., J. Interferon Cytokine Res., 1999; 19: p817-828    Non-patent Document 11: Ohtsuka, H., J. Vet. Med. Sci., 2006; 68(10): p1063-1067